The present invention relates generally to a medical-imaging compliant apparatus for adjusting a patient's head position to facilitate controlled orientation of the cervical spine during medical imaging.
Medical imaging has become an indispensable tool for the diagnosis and treatment of conditions affecting a person's cervical spine. Images of the cervical spine provide doctors with insight into such conditions as cerebral spinal fluid flow patterns, nerve compression, spinal instability and intervertebral disk damage. Diagnosis of these, and other conditions, often requires that images of the patient's spine be taken while the spine is rotated about its axis or while undergoing flexion/extension. These specific configurations may need to be accurately recreated during subsequent imaging to facilitate diagnosis and treatment.
Medical imaging technologies, such as those used in magnetic resonance (“MR”) imaging and computed tomography (“CT”) imaging, are extremely sensitive to the amount and type of material, as well as its location in relation to the area to be imaged, of any equipment present during imaging. MR imaging uses a strong magnetic field to polarize nuclei whose position is then detected by special coils. The presence of conductive or magnetic material disrupts the detection and thus spatial encoding of the signals—ultimately degrading the clarity of the image and the information the doctor is able to learn from the MR scan.
CT imaging uses X-ray attenuation to reconstruct a three-dimensional image. Given that different materials and tissues cause varying attenuation of the X-rays used in a CT, it is critical that any support structure introduced into the scan be radiolucent, meaning the material does not substantially scatter or block the X-rays causing artifacts in the images.
Conventional wisdom has lead inventors to design cervical rotation devices that remove supporting structure from the area to be imaged to reduce image artifacts. When the material is unable to be removed from the imaging area, plastics are commonly used because of their low interaction with both MR and CT imaging machines. The removal of structure from the imaging area along with the use of imaging compliant materials is advantageous as it reduces the amount of interference caused by the fixture, therefore providing a more informative image.
One previous design consists of a head cradle shaped as a half-cylinder with one open end and one closed end. A pin mounted to the closed end supports the head cradle. The other end of the pin is rotatably mounted to the back of a frame having support legs extending on the left, back, and right of the head cradle minimizing the portion of the support structure within the imaging area of the head cradle. The design is effective at removing the majority of the structure from the imaging area; however, a single pin supports the entire weight of the patient's head. This cantilevered design places a tremendous amount of stress on the pin making it less suited for construction from CT and MR imaging compliant materials such as plastic. Additionally, orientating a patient's head is difficult given the high load placed upon the pin at the axis of rotation.
Another design incorporates an outer ring with radial slots around a portion of the circumference. A head cradle shaped as an open-ended half-cylinder has two collinear pegs extending radially outward from the head cradle. The head cradle is suspended within the large outer ring by placing the two pegs through the radial slots in the outer ring and independently clamping each peg in place. This design eliminates the high stresses placed on the single pin in the previous design, but the head cradle may be difficult to rotate because the weight of the patient's head acts to wedge the pegs downward in the radial slots.
It is critical that the portion of the spine being imaged remains immobile in the desired orientation throughout imaging. Common techniques to reduce head movement during imaging involve combinations of strategically located straps, clamps, and blocks. These techniques are time consuming and cumbersome because a health care professional must configure the individual pads and straps. The sight of clamps and straps may add to patient anxiety.